The present invention relates in general to flame-monitoring equipment, and in particular to a new and useful video camera based measuring instrument which provides real-time displays of an object along with a two dimensional temperature map of the object which is determined using two-color pyrometry.
Optical pyrometry is a measurement technique in which the temperature of an object is determined based on the magnitude of the thermal radiation emitted by the object. In general, the radiant energy emitted by an object is measured at one or two wavelengths. These measured spectral energies are related to the temperature of the object using Planck's radiation function: EQU W(.lambda.,T)=.epsilon.*C.sub.1 /(.lambda..sup.5 *[exp{C.sub.2 /.lambda.T}]-1)
where:
W(.lambda.,T)--spectral radiant emittance of object PA1 .epsilon.--emissivity of object PA1 .lambda.--wavelength of radiation PA1 T--temperature of object PA1 C.sub.1, C.sub.2 --constants
Most optical pyrometers are single point devices which provide a temperature that represents a spatial average. Spatial distribution of temperature can be determined only through a series of single point measurements as disclosed in U.S. Pat. No. 4,644,173 assigned to The Babcock & Wilcox Company. In this reference, improvements in spatial resolution were achieved by using optical fibers and photodiode arrays to provide multiple and near simultaneous measurements of temperature. This technique provides improved spatial resolution in temperature measurement, but is limited by the number of simultaneous measurements.
Devices which provide spatially-resolved, two-dimensional temperature maps have been developed. These are of two types: scanning devices which use a single detector in concert with scanning optics that permit measurement of the spatial distribution of spectral energy, and a video camera type which can provide a two-dimensional spectral image.
The sophistication of these devices varies greatly. In some instances, the two-dimensional image of spectral energy is used only to infer regions of hot and cold. With other devices, the temperature at some point in the spectral image must be known (a benchmark) before the two-dimensional temperature map can be determined. Scanning devices have demonstrated the capability to generate two-dimensional temperature maps without the need for this type of benchmarking. All of these devices are analogous to single color pyrometers in that the spatial distribution of intensity is measured at only one wavelength.